Air is a far more testing environment than the road; for example, the temperatures and pressures are extreme, safety considerations are paramount, and the engines dwarf those of Formula One. To meet these demands, aviation fuels have to achieve three high standards: they must be powerful, protective of the engine, and environmentally safe. This throws down three technological gauntlets for aviation fuel suppliers: formulation, purity and testing.
The best suppliers are those that can deliver this in a market that is financially complex and logistically demanding yet still tailor their product to a client’s specific requirements. It is not like filling up at a service station; nevertheless, here are some of the main categories of fuel.
Avgas is chemically close to petrol; however, unlike petrol for cars, it still usually contains lead. For this and other reasons, it is in decline; however, it is still often required by Wankel and other reciprocating engines. Many light aircraft have been successfully converted to use the non-leaded jet fuel that powers turbine aircraft.
This term usually refers to blends based on high energy naphtha kerosene. Although this is similar to the paraffin once used for heating in the UK, long carbon chains make it resistant to low temperatures. It also has a higher flashpoint, which makes it safer. Many formulations based on jet fuel are available for turbines and compression ignition engines.
Jet A and Jet A-1 are examples. These kerosene-based formulations have a high flashpoint of about 38°C, making them store well and safely, and good cold tolerance (-40°C and -47°C respectively).
In contrast, Jet B and TS-1 are examples of kerosene-based fuels with even better cold tolerance but lower flashpoints and therefore higher volatility. They are the preferred choice in extra cold regions of the world, such as Canada, Russia, Central Asia and Antarctica. The TS-1 flashpoint is 28°C and the freezing point below -50°C.
A military blend called D. Eng RD 2494 was adopted for British civilian use and re-named DEF STAN 91-91. It is now almost a standard for British airlines, with performance easily matching Jet A-1. Fuel suppliers can tailor these basic products for a particular customer. Additives can often achieve more power, engine protection, fuel longevity, burn efficiency, and cleaner emissions.
The aviation fuel industry is at the forefront of efforts to develop alternative fuels. Some of these are radical, such as using liquefied natural gas, but the main focus is on introducing sustainable biofuels.
Biofuels are often derived from vegetable oils but can also be extracted from waste plastics. The crops suitable to produce biofuel can often be grown on marginal land unsuitable for food production, are carbon-neutral, and they are inexhaustible – unlike fossil fuels. Extracting fuel from waste helps to alleviate landfill and pollution issues. Biofuel blends are already widely available.